Aqueous slurries of coal particles become available at a number of places, such as at a mine site where coal is mined with the aid of water and at the end of a pipeline wherein the coal is transported with water as the carrier liquid. These slurries generally contain coal particles of different sizes in a more or less continuous spectrum from small to large. In order that the slurry is easily flowable, the total amount of solids therein is limited, e.g. to 50 percent by weight. For such purposes as shipment or combustion, the amount of water in the slurry will then be too high.
Accordingly, the slurry has to be treated to the extent that one or more products are obtained that contain less or considerably less water. A problem in this respect is that large and small particles tend to behave quite different in most dewatering processes, and in fact, require different methods of dewatering. The small particles are more difficult to dewater than the large particles, and when the large and small particles are separated and separately dewatered, the small particles require an expensive dewatering process and dewatering give rise to dusting problems, remixing of large and small particles then being difficult or impossible.
The present invention proposes a process wherein the above problems are solved and whereby a dewatered load of coal is obtained from an aqueous slurry of coal particles in an economic way.